KeyDB.cfg is a vital file for users who want to decrypt and rip 4K UHD Blu-rays using MakeMKV. It acts as a database of "VUK" (Volume Unique Keys) that allows the software to bypass copy protection on newer discs.
However, a historic exemption granted by the U.S. Copyright Office allows the circumvention of DRM on Blu-ray discs specifically for the purpose of creating fair-use backups, educational use, or accessibility (commentary). keydbcfg makemkv
Now keydbcfg can inspect live progress:
keydbcfg hgetall makemkv:job:/dev/sr0 Built-in decryption for many discs